It is my understanding that todays commercial Red Swordtail is a hybrid. They are generally a cross between Xiphophorus hellerii and a Xiphophorus maculatus(Southern platy). Sometimes they also use X.variatus to cross with the X.hellerii. If I remember correctly, they are prone to mutations/melanoma and that way you can get some new color variations within a few generations. They are now using some of them in cancer research.I have Xiphophorus montezumae that I keep in my temperate palludarium with water temps varying from the low 50's to the high 70's. I also have Xiphophorus xiphidium 'Rio Purification' and they require a higher temperature. As with most things, you'll get better results if you look under the Latin name. Scott

Hi
The Latin name doesn't tell me much as a red swordtail
is a cross between to separrate species. there is no such thing as a wild red swordtail,though there are wild red platies.
I've been raising what are called "Red wag swordtails "
in 3 pools since 1982 so all are related .Still producing about 80 percent RW swords lol. I once read an article that stated that there are no natural hybrids even though the ranges of the two fish overlap.
Was curious, if this was true ,why my fish have not reverted back to the "wild green " color and why are they not sterile.?
Even if you figure only 3 generations per year I have at least 70 generations lol Need some history of how the strain was firsst produced. gary

I'll see what else I can find! Have a look at this travel log. I'm not sure, but you might get something useful out of it!

Here is a link that might be useful: In Search of the 'Wild' Red Swordtail

Another name to use while looking is the Green swordtail! It is still a Xiphophorus hellerii, but you might find other references closer to what you want. It seems as though the key to finding information is creative searching and sometimes creative spelling as well! Obviously, with your interest in exotic plants, you know how frustrating it can be to research names, both Latin and common! The Green Swordtail was brought to Europe at one point, where many varieties were produced, that is probably your best bet on the origins of your Red wags. (God only knows what is coming out of the Asian factories these days!You're lucky that they aren't injected with red dye!) Perhaps the falure to revert back to the wild color could be because there is no reason to do so!(Lack of predator influence on color determination?) It's just a random thought! I really don't know about the lack of sterility. It could be that your initial population was high enough that the gene pool is able to absorb it without adverse effects. Also, I have understood that sometimes there aren't natural hybrids because normally there is a greater drive to mate with what either looks like you or gives off the correct signals and responses. In an artificial environment, who knows, it could be a free for all! There are several studies about female preference for male sword length in the green swordtail. There could be also a preference for other characteristics that are not generally desirable for a wild fish. Much of the signaling during male courtship display in these species is visual. I've read that female Xiphophorus prefer males with swords, whether or not the males of their species have swords!
Cut and paste this to your search program "Predator exposure alters female mate choice in the green swordtail." There is some additional research going on that might explain your question about the lack of reverting color. I found this after I already guessed that the lack of predators could be a major factor. The study by Jerald B. Johnson is the one that I'm refering to. Scott

Here is a link that might be useful: Courtship and Mate Choice in Fishes